Glad you're back out there. I know what you mean about neck muscles - when I was riding my tri bike for the STP, my neck and back often hurt more than anything else on training rides. I used to rotate my head left and right a few times, sit up and flex my back every 30 mins or so, and that seemed to help.
Or perhaps some of those neck exercises the heavier guys would do so they would have bigger necks to pass the tape test? Now there's a mental picture...